Emulsion polymerization is the most commonly used method for preparing a fluorine-containing dispersion. That is to say, water, initiator, surfactant, fluorine-containing monomer and necessary additives can be added to a pressure vessel and reacted at 0° C.˜150° C. under a certain pressure to produce a fluorine-containing dispersion. In the prior art, PFOA (Pentadecafluorooctanoic Acid) or the salts thereof is often used as a surfactant.
In the recent studies, it is found that the residue of PFOA or the salts thereof in the product or the loss during the manufacturing process will eventually enter the biosphere. It is shown that PFOA or the salts thereof exist in the groundwater, in the surface water and in the sea as well as in the blood of all wild animals and human body. For the human being, PFOA or the salts thereof can be transfused to the infant through the umbilical cord and be accumulated in its body. Although no specific results show that it is harmful to human health, PFOA or the salts thereof is highly stable and is difficult to degrade in natural environment. Currently, it has not been demonstrated that it would decompose in natural environment and in organic body; however, animal experiments show that high doses of PFOA can cause cancers, embryo deformities and other diseases. Hence, reducing or eliminating the use or residue of such substance is of practical significance.
In the manufacturing process of the fluorine-containing aqueous dispersion, other substances are tried to replace PFOA or the salts thereof as surfactants. U.S. Pat. No. 3,271,341 of Dupont Company of America disclosed that the analogues of F—(CF2)m—O—[CF(X)—CF2—O]n—CF(X)-COOA was used as surfactants in emulsion polymerization of fluorine-containing alkenes; Patent WO 2007,011,631 of 3M Company of US disclosed the use of CF3—O—(CF2)3—(O—CF(CF3)—CF2)z—O-L-Y type polyether in emulsion polymerization; U.S. Pat. No. 6,878,772B2 of Solvay Company of Belgium disclosed bifunctional fluoropolyether was used as a surfactant.
This invention provides a peroxidic fluoropolyether carboxylic acid or its salts and use thereof as surfactants in emulsion polymerization of fluorine-containing monomer.